Step 1In a medium bowl, toss the shrimp with the contents of 1 can of beer. Cover and refrigerate 1 to 2 hours.
Step 2In a small bowl, combine the Old Bay, paprika, celery salt, kosher salt, cayenne pepper and ground ginger. Set aside.
Step 3With a sharp knife, cut the head of garlic (with the peel) in half crosswise. In a large stockpot heated over medium heat, add 2 tablespoons olive oil. Add the chopped onion, all of the garlic, the rosemary and chile de arbol and cook, stirring occasionally, until softened, about 10 minutes. Add 3 tablespoons of the spice blend and the juice of 1 lemon, stirring. Add the remaining beer and reduce the liquid by three-fourths over high heat, about 20 minutes.
Step 4Drain the shrimp and add them to the pot. Cover the pot, and steam just until the shrimp are cooked, 4 to 5 minutes over high heat. The shrimp will be ready when they turn white; be careful not to overcook them.
Step 5Remove the shrimp to a large baking sheet with sides and drizzle with remaining olive oil. Sprinkle over more of the spice blend to taste (we used 2 tablespoons). Sprinkle with the parsley and the juice from the remaining lemon. Serve immediately.